It has been considered that the measurement of the left atrial pressure (LAP) is important for the evaluation of the cardiac performance in addition to the measurement of the blood pressure and the cardiac output. Therefore, various techniques for measuring the left atrial pressure have been developed. For example, a technique has been known that inserts a catheter provided with a balloon at the tip into the esophagus, inflates the balloon at a position adjacent to the left atrium, and measures the internal pressure of the balloon to measure the left atrial pressure, taking account of the fact that the esophagus is situated on the back side of the left atrium (see JP-A-2006-142038, for example).
According to the above technique, however, since it is necessary to indwell the balloon in the esophagus, the burden imposed on the subject increases.
Pulmonary artery catheterization, ultrasound Doppler echocardiography, and the like have also been known as a technique for measuring or estimating the left atrial pressure. However, these techniques also have a problem.
For example, when implementing pulmonary artery catheterization, a catheter is inserted into the pulmonary artery through the jugular vein and the right atrium. The blood flow is temporarily blocked by wedging a balloon provided just proximal to the tip of the catheter into the pulmonary artery, and the static pressure applied to the end of the catheter is measured. The static pressure (i.e., pulmonary capillary wedge pressure (PCWP)) thus measured is used as a substitute for the left atrial pressure (LAP). This technique achieves high measurement accuracy, but is very invasive. Moreover, skill is required for the operator to insert the catheter into an appropriate position.
Ultrasound Doppler echocardiography (transthoracic ultrasound Doppler echocardiography) is a technique that estimates the left atrial pressure (LAP) using the ratio (E/e′) of the early diastolic peak (E) of the mitral valve orifice blood flow waveform to the early diastolic peak (e′) of the mitral annulus motion velocity waveform. However, recent studies have revealed that the ratio (E/e′) does not necessarily have a correlation with the pulmonary capillary wedge pressure (PCWP) in various cardiac diseases.